Locating and tracking surface, near-surface, and underwater platforms continues to be a concern of government and private organizations. Traditional methods of sea-going platform tracking rely on active signals or known information about a received signal. For example, sonar tracking relies on an active signal sent from a known location. The active signal is reflected off one or more sea-going platforms, such as a ship, and returned to the source of the active signal. Although sonar tracking provides accurate location information, sonar tracking relies on an active pulse that can be easily detected by sea-going platforms and which provides location information on the signal source.
Ultra-short baseline (USBL) positioning allows underwater acoustic positioning for known acoustic signals. A transceiver is mounted on ship and transmits a known signal. The known signal is received by a remote device, such as an underwater remotely-operated vehicle (ROV). The remote device responds with a return signal which is detected by the transceiver on the ship. The return time and the return angle are calculated for the received signal and the position of the remote device determined. Traditional USBL requires a known signal transmitted from a known location. U.S. Pat. No. 7,362,653, issued on Apr. 22, 2008, and entitled “Underwater Geopositioning Methods and Apparatus” is incorporated herein by reference in its entirety. Because a known signal must be sent and received, USBL does not provide tracking capabilities for unknown signals or uncooperative sea-going platforms.
What is needed is a system for passively tracking sea-going platforms based on unknown broadband acoustic signals generated by the sea-going platform.